1. Field of the Invention
The present invention relates to an image-forming apparatus that forms an image by transferring a toner image formed on an image carrier onto a recording medium and a control method for controlling the image-forming apparatus.
2. Description of the Related Art
In printers, copy machines, etc., using electrophotographic technology, input image data is converted into electrical signals and a laser is driven on the basis of the obtained electrical signals, so that an electrostatic latent image corresponding to the image data is formed on a photosensitive member. The thus formed electrostatic latent image is visualized as a toner image by a developing device and is then transferred onto a recording sheet.
In monochrome printers in which images are formed using black developer (toner), the density of the images greatly affects the printing quality. Similarly, in color printers in which color images are formed using yellow (Y), magenta (M), cyan (C), and black (K) toners, the density of the images formed by the toner of each color greatly affects the printing quality. Accordingly, Japanese Patent Laid-Open No. 6-11965 discusses a structure in which a correction pattern used for density correction is formed on a recording sheet every time a predetermined number of recording sheets are subjected to printing. The thus formed correction pattern is optically read and the density of image data is corrected on the basis of a signal obtained by optically reading the correction pattern, thereby maintaining high image quality.
According to Japanese Patent Laid-Open No. 6-11965, even when continuous printing is performed, the density correction sequence is executed every time the predetermined number of recording sheets are subjected to printing in order to maintain the printing quality. However, since the timing at which the density correction sequence is performed depends on the number of recording sheets that are subjected to printing, this timing does not always match the timing at which the density correction is required in practice. More specifically, even if the density correction is necessary, the density correction sequence is not executed until the predetermined number of recording sheets are subjected to printing. Therefore, there is a risk that the quality of the printed image is reduced during the printing operation. In addition, if the predetermined number of recording sheets are subjected to printing even though the density correction is not required, the density correction sequence is unnecessarily executed. In such a case, the toner and the recording sheet are wasted and the operating cost is increased as a result. In addition, since printing cannot be performed while the density correction sequence is being executed, the productivity is largely reduced when the density correction sequence is performed unnecessarily.